Radiological Hazard Parameters Research Articles

Spatial distribution and lifetime cancer risk due to naturally occurring radionuclides in soils around tar-sand deposit area of Ogun State, southwest Nigeria

Anthropogenically enhanced naturally occurring radionuclides 238U, 232Th and 40K present in the tar-sand soil samples were measured by gamma ray spectrometer using a highly shielded NaI (TI) detector with the aim of evaluating the environmental radiological hazards. Mineralogical analysis and characterization was carried out using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. The results obtained showed that the average activity concentrations of 238U, 232Th and 40K ranges from BDL↔76.00 ± 12.00, BDL↔204.48 ± 13.02 and BDL↔755.6 ± 40.15 Bqkg−1 respectively. Eleven other radiological and hazard parameters were estimated to know the complete hazardous nature of the samples. The values obtained for radionuclides and all its associated radiological and health hazard parameters were all higher than the world's average set by UNSCEAR. Five different minerals were identified and characterized as major and minor minerals. The mean radionuclides activity concentrations, radium equivalent and dose rate of measured radionuclides were compared with other literature values. RESRAD computer code was used to calculate the probability of excess lifetime cancer incurred by dwellers of the tar-sand deposit site, the level of which was determined to be 2.3 × 10−3(2310000). Spatial distribution of natural radionuclides in the study area was also investigated for radioactivity disequilibrium. Multivariate statistics were applied to establish the effect of mineralogy on radionuclides activity. Therefore, the tar-sand soil samples are considered to pose serious radiological hazard and cancer risk to human through the multiple routes of exposure and significant soil remediation action need to be taken for future use of the soils.

Measurement of radioactivity concentration in soil samples around phosphate rock storage facility in Richards Bay, South Africa

Mining, mineral processing and industrial activities have long been linked to increased levels of radioanuclides in soil in their vicinity. In this work, concentrations of naturally occurring radionuclides in soil samples collected around a rock phosphate storage facility in Richards Bay in South Africa were determined. A total of 90 soil samples were collected and analyzed for 238U and 232Th using neutron activation analysis and 226Ra and 4 K using a HPGe detector. The results revealed the average radioactivity concentrations of 238U, 232Th, 226Ra and 4 K in soil samples collected around the rock phosphate storage area were 28.26 ± 11.40, 29.64 ± 11.50, 32.18 ± 11.50 and 146.77 ± 63.30 Bq. kg−1, respectively, which are higher than the corresponding values of 22.26 ± 8.60, 23.09 ± 9.80, 26.52 ± 11.50 and 117.82 ± 10.04 Bq. kg−1 in soil samples from the control area about 2.0 km–4.5 km away from the rock phosphate storage facility. Furthermore, the all radiological hazard parameters (i.e annual effective dose equivalent, annual gonadal dose equivalent, the absorbed dose rate in air, the radium equivalent activity and the external Hazard Index) investigated in this study were below the maximum recommended safety limit. The observed 238U, 232Th, 226Ra and 4 K levels indicate contributions from anthropogenic activities with no significant health risks to humans or to the environment. Hence, in terms of terrestrial gamma radiation from soil, rock phosphate storage within this area does not pose any significant radiation hazard to the workers and dwellers.

Assessment of secular equilibrium and determination of natural and artificial radionuclide concentrations in the zone surrounding the site of the first nuclear reactor in Jordan

High-resolution gamma-spectrometry and ICP-MS measurements were utilized to confirm the validity of secular equilibrium among the identified natural radioactive progeny of 238U and 232Th series. The measurements of 238U, 232Th, and 40K concentrations, in the soil within 2 km range around the first nuclear reactor in Jordan, were close to the worldwide average levels. Among artificial radionuclides, only 137Cs was detected but with very low traces. The dose rate and radiological hazard parameters were found to be close to worldwide average values and below the recommended limits. Our results indicate that secular equilibrium is unperturbed within and around the uncontaminated reactor site.

An overview of the ecological half-life of the 137 Cs radioisotope and a determination of radioactivity levels in sediment samples after Chernobyl in the Eastern Black Sea, Turkey

Abstract A study which determined the activity concentration of 137 Cs in sediments contaminated by effluents from the Chernobyl accident which had collected along the coast of the Eastern Black Sea region in Turkey was carried out in 1993. Marine sediment samples were collected in 2015 from the same fifteen sampling points, and the activity concentrations of 226 Ra, 232 Th, 40 K and 137 Cs were determined for the sediment samples. The activity concentrations ranged from 10.94–25.95, 12.14–33.05, 265.74–459.89 and 2.08–37.45 Bq kg − 1 for 226 Ra, 232 Th, 40 K and 137 Cs respectively. The results showed that there was a steep decline in 137 Cs within the sediment at most of the sampling sites from the Eastern Black Sea region during the 22-year period, except for two sites at which the measured levels were much higher. This may be the result of the combined effects of radioactive contaminant entry into this area from rivers, environmental changes and nuclear testing between 1993 and 2015. Furthermore, the ecological half-life (EHL) of the 137 Cs radionuclide was estimated for the sediment samples, and radiological hazard parameters such as the absorbed dose rate in air (D), the annual effective dose equivalent (AEDE) and the excess lifetime cancer risk (ELCR) were calculated and compared with the international recommended values. It was shown that these sediments do not present any significant health risk for humans in this area.

Estimation of natural radioactivity in local and imported polished granite used as building materials in Saudi Arabia

Measurements of natural radioactivity in local and imported samples of commercial granites used in Saudi Arabia were carried out by using gamma-ray spectroscopy with hyper-pure germanium detector. The activity concentrations measured of granite samples were determined for 226Ra(from 1.53 to 77.16 Bq kg−1), 232Th (from 0.51 to 89.82 Bq kg−1) and 40K (from 19.47 to 1632.37 Bq kg−1). The corresponding average activity concentrations for 226Ra,232Th and 40K were 28.82, 34.83 and 665.08 Bq kg−1, respectively. The radiological hazard parameters (radium equivalent, gamma index, external index, internal index, absorbed dose and annual effective dose) were calculated to assess the radiation hazards associated with granite samples. The obtained results are lower than the recommended limits. The results were compared with the published data of other countries. The measurements will help in the development of standards and guidelines for the use and management of these materials.

Potential effect of natural radionuclides in riverbed sediments: a statistical approach based on granulometric and magnetic mineral differences

South India is one of the regions in the world that has the highest background radiation levels. In this region, river sediments are used in large quantities as building material. Therefore, the knowledge of the radionuclides distribution in such sediments is important for assessing their potential adverse effects on humans residing in buildings made of sediment material. For this goal, we focus on the determination of the natural radioactivity levels and magnetic properties in sediment samples collected from 33 locations along the southwestern Bharathapuzha river originating from the Anamalai hills. The sediment samples were subdivided into two categories according to particle size. It is observed that the average activity concentrations of 226Ra, 232Th, and 40K in sediment samples varied greatly with granulometric and geological differences. The average values of 226Ra, 232Th, and 40K and its associated radiological hazard parameters for category II samples (particle size between 149 μm and 2 mm) were lower than category I sediment samples (bulk samples). Moreover, the average radionuclide activity concentrations (except for 40K) and the calculated radiation hazard parameters are higher in the lowland region compared to the highland and the midland regions. The mass-specific magnetic susceptibility values ranged widely along the river, as well as between physiographic regions, e.g., average values for category I sediment samples were 950.2 × 10−8, 351.1 × 10−8 and 131.8 × 10−8 m3 kg−1 (for high-, mid- and lowland regions, respectively). Differences between physiographic regions and sediment fractions from both radioactivity determinations and magnetic parameters were analyzed with statistical tests and multivariate analysis, which showed the advantages of using both independent techniques.

Mineralogical and Radiological Micro-Analysis of Raw Sands and Their Processed By-Products for Land Reclamation Applications

In this study, forty samples of different types of raw sands, magnetite, green silicate and processed mixture of ilmenite, magnetite and green silicates have been mineralogical and radiometrically investigated after preparation. Determination of the mineral contents, radioactivity levels and their corresponding environmental impacts was also carried out. The radioactivity: 238U, 232Th, 226Ra and 40K, of these samples are of naturally occurring origin. The EDX analysis was applied for identification of trace elements in the samples. The microscopic investigations of the samples indicate that the black sand samples are economically rich in heavy minerals such as ilmenite, magnetite, zircon, rutile and monazite; in addition to leucoxene. While the processed and unprocessed green silicate contain ilmenite, zircon, sphene, monazite and calamine with quartz and other silicate minerals. The highest values of activity concentrations of 238U, 232Th, 226Ra and 40K were observed in black sand, processed and unprocessed green silicates samples. These high radioactivities are attributed to the presence of zircon, monazite and sphene. The radiological hazard parameters; the absorbed dose rate (D), annual effective dose equivalent AEDE, radium equivalent activity Raeq, external hazard index Hex, internal hazard index Hin and gamma activity concentration index Iγ of the studied samples were estimated. The results obtained were tabulated, evaluated, interpreted and discussed.

Natural Gamma Radiation in Rocks from Kerri-Kerri Formation, Northeastern Nigeria

In a study on uranium favourability in Nigeria, it was suggested that the Kerri-Kerri Formation located in the Upper Benue Trough, Northeastern Nigeria is a potential host of uranium mineralization, hence the need to assess the level of natural gamma radiation from the rocks of the area. Laboratory γ-ray spectrometric analysis was carried out with a HPGe detector by (EG & G Ortec Inc.) at the Center for Energy Research and Training, Ahmadu Bello University, Zaria. Thirty six (36) rock samples were collected from the study area from which nine (9) composite samples were formed for the laboratory γ-ray analysis. The mean concentrations of the radionuclides 238U, 232Th and 40K were 26.9988 Bq/kg, 61.9131 Bq/kg and 91.7042 Bq/kg respectively. The mean absorbed dose rate was 15.646 nGyh−1 which is lower than the world average value of 51.5 nGyh−1. The average internal and external hazard indices were found to be 0.404 and 0.331 respectively which are lower than the acceptable limits of <1. The mean radium equivalent (Raeq) value was 122.60 Bq kg−1 which is well within and less the permissible limit of 370 Bq kg−1. Since the radiological hazard parameters are all lower than the permissible limits, the study area can be considered as safe due to natural gamma radiation and the rocks of the area can be used safely for building and construction purposes.

English

Thirty-nine Arabian and Turkish coffee powder samples purchased from various markets in Saudi Arabia were analyzed by High Pure Germanium (HPGe) gamma spectrometry to determine the activity concentrations of the natural and artificial radionuclides 238U, 226Ra, 232Th, 137Cs, and 40K. All samples, (except for two samples of Turkish coffee) were found to contain a high mean content of 40K, ranging from 839.83 to 1197.11 Bq/kg and from 161.312 to 2411.215 Bq/kg for Arabian and Turkish coffee powders, respectively. The concentrations of 226Ra and 232Th were found to be 2.57 to 10.63 Bq/kg and nondetectable to 8.01 Bq/kg for Arabian coffee and nondetectable to 10.09 Bq/kg and nondetectable to 9.75 Bq/kg for Turkish coffee, respectively. Based on these values, we estimated the potential radiological hazards to consumer health from coffee powder. We determined the radium equivalent, annual effective dose rate, and external and internal hazard for each element, and all were found to be below the limit recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation. However, absorbed dose rate values for some samples were higher than the permissible limit. In all samples, the 137Cs concentration was below the detection limit. The average annual committed effective dose values reported in this study were far below the world average value of 0.30 mSv/yr for an individual. In addition, the limit for the threshold consumption rate was calculated. The statistical methods were applied to study the relationship between all the calculated natural radionuclides and their hazard parameters. Results indicated that the use of these types of coffee had no significant radiological health risks. This study may contribute data on coffee powder for formulating regulations related to radiological health care. Key words: Arabian and Turkish coffees, natural radioactivity, radiological hazard parameters.

Assessment of radiological parameters of soil in Kogi State, Nigeria

ABSTRACTThe natural radioactivity levels of soil samples collected from four local government areas in Kogi State, Nigeria were measured using a hyper-pure germanium detector, and the radiological hazard parameters associated with them were estimated. The measured concentration ranged from 7.82 ± 0.63 to 82.22 ± 1.99 Bq kg−1 for 238U, 11.05 ± 1.10 to 114.86 ± 4.72 Bq kg−1 for 232Th, and 3.38 ± 0.50 to 1272.20 ± 23.36 Bq kg−1 for 40K. Omala local government was found to have the highest concentrations of 238U (44.31 Bq kg−1) and 232Th (52.13 Bq kg−1), while Ajaokuta has the highest concentration of 40K (711.72 Bq kg−1). The lowest activity concentrations of 238U and 232Th were measured from soil samples collected from Ankpa local government area and 40K from Dekina local government area. It was noted that the activity concentrations of 40K were generally low for all the areas investigated except for Ajaokuta areas. The radium equivalents calculated for all the locations were observed to be lower than the radiation protection regulatory body reference value of 370 Bq kg−1. The radiological parameters estimated for most of the locations compared well with world average values, except for Odogba-okaba, Salem University, Forest, Nepa, Gerugu, Niger Bridge, Igaliwu, Ijeke-ogane, Bagana, and Abegikolo villages, whose values exceeded the recommended limit. This may suggest that those living or working in these areas may be exposed to higher radiation burden from the natural radionuclides.

Assessment of natural radioactivity in cements used as building materials in Turkey

The radioactivity concentrations of 226Ra, 232Th and 40K in 42 samples from different types of cements produced in Turkey were measured using gamma-ray spectrometer. The determined values were 18–143 Bq kg−1 (226Ra), 5–66 Bq kg−1 (232Th) and 142–540 Bq kg−1 (40K). Additionally, the calculated radiological hazard parameters such as absorbed dose rate, annual effective dose, radium equivalent activity, the external hazard, activity and alpha indices were found to be in the range of 38–158 nGy h−1, 188–776 µSv year−1, 41–182 Bq kg−1, 0.11–0.49, 0.15–0.65 and 0.09–0.71, respectively. Finally, the results were statistically evaluated and compared with the reported data in other countries and the international standard values given by European Commission and UNSCEAR.

Assessment of radiological hazards in the industrial effluent disposed soil with statistical analyses

Soil is the most important source of natural radiation which can pass on to the food chain and the air, contributing to the internal dose received by the population. Human activities can modify the natural concentrations of radionuclides by the release of residues or effluents to the environment, which cause the accumulation of radioactive elements. In this study, the radiological hazard parameters due to the natural radioactivity, such as, Radium equivalent activity (Ra_eq), Representative level index (RLI), Activity utilization index (AUI), Absorbed dose (D), Annual Effective Dose equivalent (AEDE), Annual gonadal dose equivalent (AGDE), External hazard index (Hex), Internal hazard index (Hin) and Excess lifetime cancer risk (ELCR) are assessed from the sugar industrial effluent disposed soil. The calculated radiological parameters are compared with that of soils around different industries across the world. The recorded average value of AUI and ADGE is 0.713 and 316.72 μSv/y, respectively, are higher than the globally approved values (0.07 and 300 μSv/y, respectively). Further, the average values of RLI and ELCR are closer to the world average values. The Pearson correlation analysis and cluster analysis are employed to analyse the data and identify the existing relationships between the radiological hazard parameters with the natural radionuclides.

Assessment of radiological hazard parameters due to natural radioactivity in soils from granite-rich regions in Kütahya Province, Turkey

ABSTRACTThe analysis of natural radioactivity from 238U, 232Th and 40K in 357 soil samples collected from the province of Kütahya was carried out using a NaI(Tl) gamma-ray spectroscopy system at the Nuclear Physics Research Laboratory, Dumlupınar University, Kütahya, Turkey. The specific activities of 238U, 232Th and 40K in the soil samples were evaluated. From the activity concentrations of 238U, 232Th and 40K, the total absorbed outdoor gamma-ray dose rates and the corresponding annual effective dose rates were determined. The corresponding values of the external and internal hazard indices of all the soil samples were also calculated. The external gamma-ray dose rate at 1 m above the ground was directly measured at each collected soil sample location. The results obtained in this study were compared within the limits of values obtained in other cities of Turkey, those in other countries. Radiological maps of Kütahya Province were constructed from the results of this study.

Natural Radionuclides and Heavy Metals Concentration of Marine Sediments in Quseir City and Surrounding Areas, Red Sea Coast-Egypt

Concentrations of natural radionuclides 226 Ra, 232 Th and 40 K as well as the radiological hazard parameters were calculated in the marine sediments in three regions in Quseir city along the Red Sea coast; El-Edua area, Phosphate Harbour and north Flaminko Village. The average activity concentrations of 226 Ra, 232 Th and 40 K at El-Edua area were, 24.9±3, 19.6±2.4 and 234.5±43 Bq.kg -1 and at Quseir Harbour recorded the average activities concentrations were; 26.2±3.2, 19.4±2.8 and 458.6±164.2 Bq.kg -1 while at north Flaminko Village found to be; 25.7±6.9, 22.6±5 and 106.4±17.5 Bq.kg -1 respectively in Quseir city, Egypt. Concentrations of the metals; Mn, Zn, Cu, Pb, Ni, Co and Cd were determined by Atomic Absorption Spectrophotometry (AAS) using GBC932ver.1.1with detection limits of 0.01 ppm.

Assessment of natural radioactivity and radiological hazards in building materials used in the Tiruvannamalai District, Tamilnadu, India, using a statistical approach

One-hundred-fifty-one samples of six types of building materials were collected from different locations of the Tiruvannamalai District, Tamilnadu, and were analyzed using a gamma ray spectroscopy system. From the results, the highest values observed in the specific activities of 226Ra, 232Th and 40K were 116.1 (soil) 106.67 (sand) and 527.533 (tiles) in Bqkg−1, while the lowest values observed in the specific activities of the same radionuclides were 35.73, 37.75 and 159.83 for cement in Bqkg−1, respectively. The potential radiological hazards were assessed by calculating the radium equivalent activity (Raeq), the indoor absorbed gamma dose rate (DR), the annual effective dose rate (HR), the activity utilization index (I), the alpha index (Iα), the gamma index (Iγ), and the external hazard (Hex) and internal hazard (Hin) indices. The estimated mean value of the absorbed dose rate of 148.35nGyh−1 is slightly higher than the world average value of 84nGyh−1, and the annual effective dose in the studied samples is 0.1824mSvy−1, which is lower than the recommended limit. Multivariate statistical methods are applied to determine the existing relationship between radionuclides and radiological health hazard parameters and to identify the maximum contribution of radionuclide in radioactivity. The values of the hazard indices were below the recommended levels; therefore, it is concluded that the buildings constructed from such materials are safe for the inhabitants. The findings from this research will be useful to assess the radiation hazards of building materials in humans.

Assessments of radioactivity concentration of natural radionuclides and radiological hazard indices in sediment samples from the East coast of Tamilnadu, India with statistical approach

This paper reports on the distribution of three natural radionuclides 238U, 232Th and 40K in coastal sediments from Pattipulam to Devanampattinam along the East coast of Tamilnadu to establish baseline data for future environmental monitoring. Sediment samples were collected by a Peterson grab samples from 10m water depth parallel to the shore line. Concentration of natural radionuclides were determined using a NaI(Tl) detector based γ-spectrometry. The mean activity concentration is ⩽2.21, 14.29 and 360.23Bqkg−1 for 238U, 232Th and 40K, respectively. The average activity of 232Th, 238U and 40K is lower when compared to the world average value. Radiological hazard parameters were estimated based on the activity concentrations of 238U, 232Th and 40K to find out any radiation hazard associated with the sediments. The radiological hazard parameters such as radium equivalent activity (Raeq), absorbed gamma dose rates in air (DR), the annual gonadal dose equivalent (AGDE), annual effective dose equivalent (AEDE), external hazard index (Hex) internal hazard index (Hin), activity utilization index (AUI) and excess lifetime cancer (ELCR) associated with the radionuclides were calculated and compared with internationally approved values and the recommended safety limits. Pearson correlation, principal component analysis (PCA) and hierarchical cluster analysis (HCA) have been applied in order to recognize and classify radiological parameters in sediments collected at 22 sites on East coast of Tamilnadu. The values of radiation hazard parameters were comparable to the world averages and below the recommended values. Therefore, coastal sediments do not to pose any significant radiological health risk to the people living in nearby areas along East coast of Tamilnadu. The data obtained in this study will serve as a baseline data in natural radionuclide concentration in sediments along the coastal East coast of Tamilnadu.

Evaluation of radioactivity levels in fertilizers commonly used in the Southern USA

A study was performed to evaluate radioactive concentrations in three categories of fertilizers, phosphate (0–46–0); potash (0–0–60); and NPK (13–13–13) using gamma spectroscopic techniques. The experimental analyses indicated mean concentrations of 697 ± 15, 8.9 ± 1.0 and 47 ± 12 Bq kg−1 of 226Ra, 232Th, and 40K, respectively, in phosphate fertilizers. Potash fertilizers had the average levels of 1.1 ± 0.10, 0.40 ± 0.05, and 15,162 ± 1017 Bq kg−1 of 226Ra, 232Th, and 40K, respectively. The NPK fertilizers contained 7.45 ± 2.76, 2.63 ± 0.29, 3581 ± 601 Bq kg−1 of 226Ra, 232Th, and 40K, respectively. Based on the measured activities, the radiological health hazard parameters are assessed and compared with the U.S. acceptable dose limits.

Assessment of radionuclides in the soil of residential areas of the Chittagong metropolitan city, Bangladesh and evaluation of associated radiological risk

Soil samples from the three residential hubs of Chittagong city, Bangladesh were analyzed using gamma spectrometry to estimate radiation hazard due to natural radioactive sources and anthropogenic nuclide 137Cs. The activity concentration of 226Ra was found to be in the range 11–25 Bq.kg−1, 232Th in the range 38–59 Bq.kg−1 and 40K in the range 246–414 Bq.kg−1. These results were used to calculate the radiological hazard parameters including Excess of Lifetime Cancer Risk (ELCR). The estimated outdoor gamma exposure rates were 40.6–63.8 nGy.h−1. The radiation hazard index (radium equivalent activity) ranged from 90–140 Bq.kg−1. The average value of the ELCR was found to be 0.21 × 10−3, which is lower than the world average. Sporadic fallout of 137Cs was observed with an average value of 2.0 Bq.kg−1.

Natural and anthropogenic radioactivity levels and the associated radiation hazard in the soil of Oodalia Tea Estate in the hilly region of Fatickchari in Chittagong, Bangladesh.

Radioactivity in the soil of a tea garden in the Fatickchari area in Chittagong, Bangladesh, was measured using a high-resolution HPGe detector. The soil samples were collected from depths of up to 20 cm beneath the soil surface. The activity concentrations of naturally occurring 238U and 232Th were observed to be in the range of 27 ± 7 to 53 ± 8 Bq kg−1 and 36 ± 11 to 72 ± 11 Bq kg−1, respectively. The activity concentration of 40K ranged from 201 ± 78 to 672 ± 81 Bq kg−1, and the highest activity of fallout 137Cs observed was 10 ± 1 Bq kg−1. The average activity concentration observed for 238U was 39 ± 8 Bq kg−1, for 232Th was 57 ± 11 Bq kg−1, for 40K was 384 ± 79 Bq kg−1 and for 137Cs was 5 ± 0.5 Bq kg−1. The radiological hazard parameters (representative level index, radium equivalent activity, outdoor and indoor dose rates, outdoor and indoor annual effective dose equivalents, and radiation hazard index) were calculated from the radioactivity in the soil.

Spatial distribution and lifetime cancer risk due to gamma radioactivity in Yelagiri Hills, Tamilnadu, India

The spatial distribution of natural radioactivity due to uranium, thorium and potassium was investigated in soils from the undisturbed areas in Yelagiri Hills, Tamilnadu, India by Isodose map. The radiological hazards due to natural radionuclides content such as representative level index (RLI), activity utilization index (AUI), excess lifetime cancer risk (ELCR) and internal radiation hazards (Hin) of the soil samples in this area were calculated. The calculated radiological hazard parameters are compared with different countries of the world. The calculated range of ELCR is 0.326 × 10−3 to 1.067 × 10−3 with an average of 0.700 × 10−3 for soils. This average value of ELCR is more twice than the world average (0.290 × 10−3). A correlation analysis was made between measured dose rate and individual radionuclides, in order to delineate the contribution of the respective nuclides toward the dose rate. The U/Th concentration ratio in surface soil samples ranged from 0.05 to 1.72 with an average of 0.43 which is more higher (80%) than the world average of 0.26. The application of cluster analysis (CA) and principal component analysis (PCA), coupled with Pearson correlation coefficient analysis, were utilized to analyze the data, identify and clarify between the radiological parameters to know the existing relations. The CA and PCA results showed that the former method yielded three distinctive groups of the soil variables whereas the latter one yielded the number of variables into two factors with 94.47% variance explanation.